Highly efficient NiAl_2O_4-free Ni/γ-Al_2O_3 catalysts prepared by solution combustion method for CO methanation

摘要

Ti-doped Ni/γ-Al_2O_3 catalysts with Ti loadings varying from 0 wt% to 5 wt% were prepared in glycol by solution combustion method for CO methanation. Compared to Ni/γ-Al_2O_3 catalyst, Ti-doped Ni/γ-Al_2O_3 catalysts exhibited higher activity. In particular, an optimal Ti-doped Ni/γ-Al_2O_3 catalyst with Ti content of 3 wt% (G-3Ti) achieved almost 100% CO conversion and ～98.7% CH_4 selectivity at 300 ℃, 0.1 MPa, and a WHSV of 12,000 mL g~(-1) h~(-1) and showed good stability at 600 ℃. On analysis of characterization results, Ti species was found effectively restrict the formation of NiAl_2O_4 spinel phase, leading to a higher utilization of Ni species and thus more exposed active surfaces, which enhanced the CO adsorption capacity. In addition, the electron cloud density of Ni was increased by electron transfer from TiO_x, which could facilitate the dissociation of CO on the catalyst surfaces. Moreover, solvents (i.e., ethanol, n-propanol and glycol) also significantly affected the physical-chemical properties of the catalysts, and catalyst prepared in glycol exhibited better catalytic performance for CO methanation.